Luminescence Properties of GaAs Epitaxial Layers Grown By Liquid Phase Epitaxy and Molecular Beam Epitaxy
- PDF / 1,857,381 Bytes
- 8 Pages / 417.6 x 639 pts Page_size
- 47 Downloads / 257 Views
and Tan,
eds.
Defects in Semiconductors
457
LUMINESCENCE PROPERTIES OF GaAs EPITAXIAL LAYERS GROWN BY LIQUID PHASE EPITAXY AND MOLECULAR BEAM EPITAXY P. M. PETROFF Bell laboratories, Murray Hill, New Jersey 07974 USA ABSTRACT Al As The luminescence properties of undoped GaAs-Ga layers grown by liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) are compared for double heterostructure and multiquantum well (MQW)superlattices. Low temperature cathodoluminescence and scanning transmission electron microscopy are used to identify the main luminescence centers and in some instances establish their origin. The possible effects of the observed luminescence features on the degradation process in GaAs-Ga . l--X Al XAs laser devices grown by MBE and LPE are also discussed. INTRODUCTION One of the most intriguing problems to unravel in the field of defects in semiconductor devices has been that of the degradation phenomenon in GaAsGal.xAlxAs semiconductor lasers. The process of dislocation climb involving point defect and dislocation motion has been shown to be responsible for the rapid degradation process [1,2]. The slow degradation process [3,4] has also been attributed to motion of point defects resulting in point defect aggregates. Both the slow [3,4] and rapid degradation seem to involve point defects and their origin has been a subject of controversy. On the one hand the defects have been considered to be native to the material,
e.g.,
antisite
defects and point defect complexes, resulting from the crystal growth process [1,2]. While on the other hand their origin was associated with the The minority carrier recombination processes at the dislocation core [5,6]. present paper is a first step in addressing this problem. We have used two defect sensitive techniques: low temperature high resolution cathodoluminescence in conjunction with scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM), to analyze double heterostructures (DH) and multiquantum well (MQW)superlattices [7]. A special importance is attached to the analysis of interfaces which are thought to be possible sources of point defects [1] responsible for the rapid degradation. Furthermore, we have analyzed two types of materials grown by techniques which can yield a widely different stoichiometry; namely, liquid phase epitaxy (LPE) which gives a Ga rich growth condition, and molecular beam epitaxy (MBE) which yields layers grown under As rich conditions. We have examined the possible relationships between the rapid degradation phenomena and the defects related to crystal growth conditions in lasers made by these two different crystal growth techniques. EXPERIMENTAL Undoped GaAs-Ga1 Al As DH and MQWsuperlattice structures [7] have been grown by MBE. In ad~itfon, undoped GaAs-Ga 1 x Al As DH structures were also grown by LPE and compared to the MBE grown ones. The GaAs substrate orienChemical polishing and etching in bromine methanol and tation was (100). hydrogen peroxide-sulfuric acid and water solution were use
Data Loading...
